It is always a bit of a comfort and a relief to rediscover* that the Irish are such a foul-mouthed lot. I don't have to worry too much if I let slip a natural phrase every now and then, given that the atmosphere is fairly informal. And informality is a typical Irish quality.

The Irish have all the same "four-letter words" that we
have in America, of course. Additionally, there are a
few others, and some usages that are different. Some of these are in common with
the more general European English,
and some are uniquely Irish.

In common with European English, the Irish use "shite"
and "bollocks." "Shite" means "shit." From this latter term comes the Irish-English "gobshite,"* which basically means "shithead."

__ ___ __

Bollocks

"Bollocks," in Euro-English,* means "testicles," literally, but is used in various idiomatic expressions. The Irish have a few of their own adaptations.

In America, "bollocks" is a vaguely British term of no particular vulgar meaning. If you'd use it at all, it would likely be more of a comic-book-like verb, and likely spelled "bollix." In European English, "bollocks" is distinctly vulgar. In Ireland, it's just the way that people talk.

"Jayzus"

A note on blasphemy

While it is normal to hear casual use of the name and title of Jesus Christ, you won't generally hear the Irish abusing the word "God"  for example, "God damn," "God dammit," etc.

.

Piss

"Getting pissed," in Ireland as in broader Europe, is "getting drunk." This is an important distinction, as the phrase has different meaning in American. If you want to talk about anger, you should use the full American term "pissed off."

An important use of the word "piss," in European-English, is "taking the
piss." "Are you taking the piss?" means "are you being
sarcastic? (ironic, etc.)" To "take the piss out of
(someone)" is to lampoon them, or satirize them. It is also a way to say you took advantage of a situation, or acted cleverly in a devious way. You took the piss, getting paid for hours that you spent not working. The phrase is used broadly [& in various ways] in European English, but unheard in American. At least, I never heard it in America.

Cunt

"Cunt," in Irish-English, is the same as it is in Euro-English. Its primary use is vulgar, but not obscene. It is not primarily a rude term for "vagina" nor "bad woman," and its subject is usually not feminine at all. "Cunt" is just an irreverent way of refering to a fellow.

The word may also be used in adjectival form  "Cuntin'."

Arse

"Arse," the Euro-English word for "Ass," has its own
usages in Irish English:

Also, in common with European English, "fuck-all" in Irish English means "dick, squat, jack," as in "I got paid yesterday; today I have fuck-all."

The word "fuck," in Ireland, even has a diminutive form. "Feck" is mild. Kids can use it [with limitations] and you can say it on TV and the radio. And, of course, sometimes it's just more appropriate  in a polite situation, for example.

In other countries, you'd consider not cursing in a polite situation. In Ireland, there might be a word for the occasion.